Pass the MongoDB MongoDB Certified DBA Associate C100DBA Questions and answers with CertsForce

db.collection.getIndexes() is the mongosh method used to return the definitions of all indexes that currently exist on a collection. The result is an array of index specification documents that can show fields such as the index name, key pattern, index version, uniqueness, partial-filter settings, sparse configuration, collation, and whether the index is hidden. This makes the method useful for index audits, troubleshooting, and confirming the physical indexes available to the query planner. Option A is not a documented method for enumerating collection indexes. Option B resembles the $indexStats aggregation stage, which reports usage statistics for indexes, but db.collection.indexStats() is not the method used to list full index definitions. Option C, findIndexes(), is also not the documented mongosh collection helper. Administrators should distinguish between listing index definitions, examining index usage, and inspecting an individual query ' s winning plan: getIndexes() addresses the first requirement, $indexStats addresses usage metrics, and explain() addresses query-planner behavior. Therefore option D is the correct command for listing all indexes on the collection.

Study Guide reference/topic:Indexing and Query Optimization - index administration, index metadata, and db.collection.getIndexes().

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db.currentOp() is the mongosh helper used to inspect operations currently executing on a MongoDB server. Passing true requests a broad view that includes all in-progress operations as well as additional idle/system entries, so it can be used when the administrator wants to see the complete current-operation picture. The database-command form, db.adminCommand({ currentOp: true }), invokes the corresponding administrative command and is also valid for obtaining in-progress operation information. Option A adds a filter restricting the result to operations whose op field is " command " ; it therefore does not represent all operation types. Option B is not valid currentOp command syntax, and option E uses an all field that is not the documented special form for this helper. In modern MongoDB administration, the $currentOp aggregation stage is generally preferred for richer filtering and aggregation, but the question is testing the traditional helper and command interfaces. Therefore, C and D are the two valid choices among those presented.

Study Guide reference/topic:Performance Monitoring and Tuning - current operations, currentOp, and administrative diagnostics.

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Queryable Encryption is designed for client-side protection of sensitive fields while preserving supported query capabilities over encrypted values. With this model, appropriately configured client drivers encrypt selected fields before data is transmitted to the MongoDB server and decrypt authorized results on the client side. That architecture is well suited to highly sensitive PII such as government identification numbers, dates of birth, or regulated demographic information because the database server stores encrypted field values rather than plaintext for those protected fields. The Encrypted Storage Engine, option A, protects database files at rest but the server can still process decrypted data internally. TLS/SSL, option B, protects data while it is moving across the network, not the application field values from the database server itself. Role-Based Access Control, option C, restricts which authenticated principals can perform actions but does not itself cryptographically protect the field contents. Queryable Encryption complements, rather than replaces, TLS, authentication, authorization, auditing, and storage encryption. For the specific requirement of client-side encryption of sensitive application data, option D is the correct MongoDB feature.

Study Guide reference/topic:Security, Networking, and Encryption - Queryable Encryption, client-side encryption, sensitive fields, and key management.

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mongosh, the MongoDB Shell, is the interactive command-line environment used to connect to MongoDB deployments and perform administrative and data operations. Through mongosh, a DBA can run CRUD queries, aggregation pipelines, user and role administration, replica-set commands, server diagnostics, index operations, and many other management tasks. mongod, option B, is the MongoDB database server process itself; it stores data and serves requests but is not the interactive administration client. mongostat, option C, is a monitoring utility that reports a concise stream of server activity metrics such as operation rates, memory, connections, and queue information. mongotop, option D, reports time spent reading and writing data by namespace and is likewise a diagnostic utility rather than a general administration shell. DBAs may also use MongoDB Compass, Atlas interfaces, Ops Manager, or automation tooling depending on the deployment, but among these four command-line tools, mongosh is the one intended for broad interactive access and administration. Therefore option A is correct.

Study Guide reference/topic:MongoDB Architecture and Core Operations - MongoDB Shell, administration tools, server processes, and monitoring utilities.

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The supported mongosh helpers for replica-set membership changes are rs.remove() and rs.add(). rs.remove(hostname) removes the member whose host string matches the supplied host:port, while rs.add() adds a new member using either a host string or a member configuration document that includes a host field. Option C uses those documented methods in the required sequence: remove node 1, remove node 2, then add node 1 back. The names rs.removeNode() and rs.addNode() shown in the other options are not standard MongoDB replica-set helper methods. Membership changes must be performed carefully because modifying voting or data-bearing membership can affect majority calculations, elections, and availability. Administrators normally execute membership changes while connected to the current primary, allow configuration propagation, and verify replica-set health afterward with rs.status() or related diagnostics. If a removed data-bearing node is later re-added, it may need to synchronize depending on how far its data has diverged from the current replica-set history. Among the choices, option C is the only valid command sequence.

Study Guide reference/topic:Cluster Reliability and Data Resilience - replica-set membership, rs.remove(), rs.add(), and topology changes.

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